Brown rot, also known as bacterial wilt, is one of the most destructive diseases of potato. It has been estimated that the disease affects about 3.75 million acres in approximately 80 countries throughout the world with global damage estimates currently over $950 million per year. The disease usually occurs in the wet tropics and subtropics around the world.

The disease is caused by the bacterium Ralstonia solanacearum, previously known as Pseudomonas solanacearum. Strains of this pathogen affect more than 200 plant species in over 50 families throughout the world, including a wide range of crop plants, ornamentals, and weeds. R. solanacearum is a soilborne and waterborne pathogen, and host resistance is limited due to strain variation, thus making bacterial wilts very difficult to control.

Strains of R. solanacearum have conventionally been classified as races and biovars. Brown rot of potato is caused by either race 1 or race 3 of R. solanacearum. The race 3 biovar 2 (R3bv2) attacks plants at higher altitudes in the tropics or in temperate zones. R3bv2 is an extremely destructive potato pathogen in the highland tropics of Africa, Asia, and Latin America and has recently appeared in Europe, where it disrupted seed potato production and caused serious quarantine-related losses. In the United States, R3bv2 was listed in 2002 as a select agent plant pathogen and is now subject to the strictest biosecurity regulations.

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